Metabolism experiments; their technique and value in assessing the nutritional value of pastures

Abstract

Common methods adopted to ascertain the nutritional value or quantity and quality of grass and other foodstuffs include changes in live weight, improvement in health and production, chemical analyses, naked eye responses to fertilizers, tons per acre, and so on. Each of these methods has its limitations. Within recent years however, more attention has been devoted to bridging the gap between actual production of a foodstuff and its utilisation by the animal which, after is the final test of its suitability particular funtions. For that reason metabolism studies must now be recognised as part of any scheme, designed to improve pasture or feed production. The purpose of this pager is to discuss the value of digestability work in relation to grassland research and nutritional problems peculiar New Zealand conditions. Support for the views just discussed will be given by a brief discussion on some of the results obtained by Dr. H.E. Woodman in his pasture investigations at the Nutrition Institute Cambridge University. In this work Dr. Woodman has not only estimated total yields and the chemical composition in his pasture research, but has added considerably to the value of his results by digestibility trials thus obtaining data on quantities of the different constituents actually available to the animal. It should be obvious to all that figures for gross production are of much greater value when the percentage availability (and this includes the percentage of the food the animal is able to utilise for production of energy, heat, fat, flesh, milk etc) of the individual food constituents is also known.